The present invention relates to coin discriminating devices, particularly of the kind comprising camera means for producing an image of a surface of a coin, and processing means, operatively connected to the camera means, for analyzing the image and determining a type of the coin. The present invention also relates to a coin handling apparatus incorporating such a coin discriminating device, and to a coin discriminating method.
Coin discriminating devices, or coin discriminators, are used in e.g. coin counting/sorting machines for identifying the type (e.g. denomination) of each coin that is processed by the machine. Furthermore, coin discriminators are used in coin inspection systems for sorting out foreign coins, counterfeit coins as well as coins that are unfit for further circulation (due to e.g. excessive wear).
Some coin discriminators operate inductively by exposing the coins to an alternating magnetic field by means of one or more than one coil and by detecting a physical property of the coin in response to the magnetic field exposure. For instance, the decay of eddy currents induced in the coin may be measured and used for determining the conductivity of the coin. Furthermore, magnetic properties such as permeability may be determined, as well as dimensional information, e.g. diameter or thickness.
Inductive coin discriminators are often able to successfully identify the metallic composition of the coin, thereby allowing a determination of the coin denomination by additionally using measurement data related to e.g. the coin diameter. However, not all coin types are distinctive enough, in terms of their magnetic and electric characteristics, to allow differentiation by means of an inductive coin discriminator.
A different and considerably more expensive kind of coin discriminators is optical pattern recognition discriminators, which produce e.g. a gray-scale or monochromatic image of the coin surface and identify the coin type by image analysis methods and comparisons with stored coin reference data. Optical pattern recognition discriminators of this type are shown in EP-A-0 798 669, EP-A-0 798 670, JP-A-10105765, JP-A-09259320 and U.S. Pat. No. 5,576,825. They comprise light emitting means for projecting light onto one surface of a coin, a camera or other optical sensor means for producing an image from the light reflected from the coin, and processing means for determining a type of the coin by comparing the image with reference data related to different types of coins.
A common drawback of these prior art discriminators is that only one surface of the coin is photographed and analyzed. Whether the determination is made for the front coin surface or for the rear coin surface will be completely random; it all depends on the orientation of the coin at the moment it passes the discriminator, i.e. whether the front surface or the rear surface faces the camera. Therefore, if the photographed surface has been severely altered due to e.g. excessive wear or other mechanical damage, the determination of type will be less accurate. Furthermore, since only one of the coin surfaces is used for the determination, the discriminator may experience severe difficulties in differentiating between two individual coins of different currency or denomination, if one surface of the first coin happens to resemble one surface of the second coin.
The object of the present invention is to provide an optical coin discriminating device, which more accurately may determine the type of individual coins.
This object is achieved by providing the discriminator with two separate cameras or optical sensors for producing one image of the first surface of each coin, and another image of the second coin surface. The processor of the discriminator is arranged to analyze both images and compare them to predetermined coin reference data in order to separately determine a type of the first surface and a type of the second surface. By combining the two determined surfaces, a type of the coin may be accurately established.
An important aspect of the present invention is the realization that such a coin discriminating device may advantageously be incorporated in an advanced coin handling apparatus recently developed by the applicant. In such a coin handling apparatus only an edge portion of each coin is engaged between two rotary transport means, thereby exposing a majority of both the front surface and the rear surface to the two cameras.
Other objects, features and advantages of the present invention appear from the following detailed disclosure, from the drawings as well as from the appended claims.